/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context.weaving;

import java.lang.instrument.ClassFileTransformer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.instrument.InstrumentationSavingAgent;
import org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver;
import org.springframework.instrument.classloading.LoadTimeWeaver;
import org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver;
import org.springframework.instrument.classloading.glassfish.GlassFishLoadTimeWeaver;
import org.springframework.instrument.classloading.jboss.JBossLoadTimeWeaver;
import org.springframework.instrument.classloading.tomcat.TomcatLoadTimeWeaver;
import org.springframework.instrument.classloading.weblogic.WebLogicLoadTimeWeaver;
import org.springframework.instrument.classloading.websphere.WebSphereLoadTimeWeaver;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Default {@link LoadTimeWeaver} bean for use in an application context,
 * decorating an automatically detected internal {@code LoadTimeWeaver}.
 *
 * <p>Typically registered for the default bean name
 * "{@code loadTimeWeaver}"; the most convenient way to achieve this is
 * Spring's {@code <context:load-time-weaver>} XML tag.
 *
 * <p>This class implements a runtime environment check for obtaining the
 * appropriate weaver implementation: As of Spring Framework 5.0, it detects
 * Oracle WebLogic 10+, GlassFish 4+, Tomcat 8+, WildFly 8+, IBM WebSphere 8.5+,
 * {@link InstrumentationSavingAgent Spring's VM agent}, and any {@link ClassLoader}
 * supported by Spring's {@link ReflectiveLoadTimeWeaver} (such as Liberty's).
 *
 * @author Juergen Hoeller
 * @author Ramnivas Laddad
 * @author Costin Leau
 * @see org.springframework.context.ConfigurableApplicationContext#LOAD_TIME_WEAVER_BEAN_NAME
 * @since 2.5
 */
public class DefaultContextLoadTimeWeaver implements LoadTimeWeaver, BeanClassLoaderAware, DisposableBean {

    protected final Log logger = LogFactory.getLog(getClass());

    @Nullable
    private LoadTimeWeaver loadTimeWeaver;


    public DefaultContextLoadTimeWeaver() {
    }

    public DefaultContextLoadTimeWeaver(ClassLoader beanClassLoader) {
        setBeanClassLoader(beanClassLoader);
    }


    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        LoadTimeWeaver serverSpecificLoadTimeWeaver = createServerSpecificLoadTimeWeaver(classLoader);
        if (serverSpecificLoadTimeWeaver != null) {
            if (logger.isDebugEnabled()) {
                logger.debug("Determined server-specific load-time weaver: " +
                        serverSpecificLoadTimeWeaver.getClass().getName());
            }
            this.loadTimeWeaver = serverSpecificLoadTimeWeaver;
        }
        else if (InstrumentationLoadTimeWeaver.isInstrumentationAvailable()) {
            logger.debug("Found Spring's JVM agent for instrumentation");
            this.loadTimeWeaver = new InstrumentationLoadTimeWeaver(classLoader);
        }
        else {
            try {
                this.loadTimeWeaver = new ReflectiveLoadTimeWeaver(classLoader);
                if (logger.isDebugEnabled()) {
                    logger.debug("Using reflective load-time weaver for class loader: " +
                            this.loadTimeWeaver.getInstrumentableClassLoader().getClass().getName());
                }
            }
            catch (IllegalStateException ex) {
                throw new IllegalStateException(ex.getMessage() + " Specify a custom LoadTimeWeaver or start your " +
                        "Java virtual machine with Spring's agent: -javaagent:org.springframework.instrument.jar");
            }
        }
    }

    /*
     * This method never fails, allowing to try other possible ways to use an
     * server-agnostic weaver. This non-failure logic is required since
     * determining a load-time weaver based on the ClassLoader name alone may
     * legitimately fail due to other mismatches.
     */
    @Nullable
    protected LoadTimeWeaver createServerSpecificLoadTimeWeaver(ClassLoader classLoader) {
        String name = classLoader.getClass().getName();
        try {
            if (name.startsWith("org.apache.catalina")) {
                return new TomcatLoadTimeWeaver(classLoader);
            }
            else if (name.startsWith("org.glassfish")) {
                return new GlassFishLoadTimeWeaver(classLoader);
            }
            else if (name.startsWith("org.jboss.modules")) {
                return new JBossLoadTimeWeaver(classLoader);
            }
            else if (name.startsWith("com.ibm.ws.classloader")) {
                return new WebSphereLoadTimeWeaver(classLoader);
            }
            else if (name.startsWith("weblogic")) {
                return new WebLogicLoadTimeWeaver(classLoader);
            }
        }
        catch (Exception ex) {
            if (logger.isInfoEnabled()) {
                logger.info("Could not obtain server-specific LoadTimeWeaver: " + ex.getMessage());
            }
        }
        return null;
    }

    @Override
    public void destroy() {
        if (this.loadTimeWeaver instanceof InstrumentationLoadTimeWeaver) {
            if (logger.isDebugEnabled()) {
                logger.debug("Removing all registered transformers for class loader: " +
                        this.loadTimeWeaver.getInstrumentableClassLoader().getClass().getName());
            }
            ((InstrumentationLoadTimeWeaver) this.loadTimeWeaver).removeTransformers();
        }
    }


    @Override
    public void addTransformer(ClassFileTransformer transformer) {
        Assert.state(this.loadTimeWeaver != null, "Not initialized");
        this.loadTimeWeaver.addTransformer(transformer);
    }

    @Override
    public ClassLoader getInstrumentableClassLoader() {
        Assert.state(this.loadTimeWeaver != null, "Not initialized");
        return this.loadTimeWeaver.getInstrumentableClassLoader();
    }

    @Override
    public ClassLoader getThrowawayClassLoader() {
        Assert.state(this.loadTimeWeaver != null, "Not initialized");
        return this.loadTimeWeaver.getThrowawayClassLoader();
    }

}
